Metals are used as catalysts in a diversity of chemical processes. Ideally, it is desired to have such metals in as finely dispersed a state as possible so as to maximize catalytic activity. When metals are used in their most highly dispersed state, a batch-type process is often employed. Removal of the catalyst in subsequent processing is disadvantageous because of attending loss of metal and the necessity for a costly separation stage. Therefore, metals commonly are deposited on an appropriate supporting medium in a more discrete fashion, for example, as extrusions, tablets, pellets, etc. Utilization of the metal in such a form permits continuous processes, but it is found that the metal is not in such a finely dispersed state as is otherwise possible. Furthermore, transport phenomena become important because much of the metal is in the interior of the supporting medium and not on its surface.
A discovery of this invention is that chitin and chitosan are desirable supports for zerovalent metals which are active catalysts in hydrogenation of unsaturated organic materials. In particular, zerovalent metals can be supported on chitin and chitosan in a highly dispersed state to afford active catalysts which, when the metal is one of the Group VIII metals, are effective in hydrogenation of a variety of unsaturated organic materials, including alkenes, alkynes, and aromatic compounds. The process of hydrogenation which is the invention disclosed herein is a noteworthy addition to the arsenal of hydrogenation methods, the latter occupying a central position in commercial chemical processes.